1. Field of the Invention
The present invention relates to an expansion valve for a refrigerant disposed in a refrigeration cycle of an air conditioner, a refrigeration device or the like.
2. Description of the Related Art
Japanese Patent Laid-Open Publication No. 2000-346494 (patent document 1) discloses an example of a prior art expansion valve widely used in a refrigeration cycle of an air conditioner of a vehicle or the like.
FIGS. 3 and 4 are referred to in describing the prior art expansion valve. FIG. 3 is a vertical cross-sectional view, and FIG. 4 is an explanatory view showing the relevant portion thereof.
As illustrated in FIG. 3, an expansion valve 1 is formed of a rectangular column-shaped valve body 10, and the valve body 10 has a first passage 11 of a refrigeration cycle 4 through which the refrigerant flowing toward an evaporator 2 passes and a second passage 12 through which the refrigerant flowing from the evaporator 2 toward a compressor 3 passes, which are formed to the valve body 10 in a vertically separated manner.
The valve body 10 further has an orifice 13 and a valve chamber 15 formed to the first passage 11, a spherical valve means 20 arranged in the valve chamber 15 for controlling the flow of refrigerant passing through the orifice 13, and an adjustment screw 24 of a spring 23 for pushing the valve means 20 toward the direction of the orifice 13 via a valve member 21.
The adjustment screw 24 is adjustably screwed onto amounting hole 16 formed to a bottom surface of the valve body 10 and communicated with the valve chamber 15, and an O-ring 24a is attached to the adjustment screw 24 in order to assure that the valve body 10 is maintained airtight. This adjustment screw 24 and the spring 23 are used to adjust the opening of the valve means 20 with respect to the orifice 13.
Reference number 11a denotes an inlet port through which the refrigerant flowing from a compressor 3 via a condenser 6 and a receiver 5 toward the evaporator 2 enters, the inlet port 11a being connected to the valve chamber 15, and reference number 11b denotes an outlet port leading to the evaporator 2.
The valve body 10 has a small diameter hole 14 and a large diameter hole 14a larger than the hole 14 that are formed concentrically with the orifice 13 and penetrating the second passage 12 so as to enable a valve actuating member 40 (described later) to be disposed for providing driving force to the valve member 20 and for opening and/or closing the orifice 13 in response to the exit temperature of the evaporator 2. On the upper end of the valve body 10 is formed a screw hole 17 for fixing a power element portion 30 functioning as the heat sensing portion. A ring-shaped seal member 50 is disposed to the inner side of the large diameter hole 14a. 
The power element portion 30 is provided with a diaphragm 31, an upper cover 34 and a lower cover 35 welded to each other and sandwiching the diaphragm 31 so as to define above and below the diaphragm 31 an upper pressure actuated chamber 32 and a lower pressure actuated chamber 33, and a plug member 36 for sealing a predetermined refrigerant working as a diaphragm actuating fluid to the upper pressure actuated chamber 32. The lower cover 35 is attached by screw engagement onto the screw hole 17 via a packing 37. The lower pressure actuated chamber 33 is communicated with the second passage 12 through a pressure equalizing hole 18 formed concentrically with respect to the center line of the orifice 13.
The refrigerant vapor exiting the evaporator 2 travels through the second passage 12, and the passage 12 functions as a gas-phase refrigerant passage, with the pressure of the refrigerant vapor loaded to the lower pressure actuated chamber 33 through the pressure equalizing hole 18. Reference number 12a denotes an inlet port for the refrigerant, and reference number 12b denotes an outlet port through which the refrigerant exits toward the compressor 3.
Further, at the center of the valve body 10 is disposed a rod-shaped valve actuating member 40. The valve actuating member 40 has a top portion 42 formed in the shape of a large-diameter disk disposed within the lower pressure actuated chamber 33 and that comes into contact with the center area of the lower surface of the diaphragm 31. The valve actuating member 40 is passed through the second passage 12 and the large diameter hole 14a and is slidably disposed within the small diameter hole 14, for transmitting the exit temperature of the refrigerant from the evaporator 2 to the lower pressure actuated chamber 33 and to provide driving force by sliding in the vertical direction in response to the displacement of the diaphragm 31 accompanying the difference in pressure between the upper and lower pressure actuated chambers 32 and 33. Furthermore, the lower portion of the valve actuating member 40 is formed as a small-diameter portion 43, and the lower end thereof is in contact with the valve means 20.
Therefore, the valve actuating member 40 extending from the lower surface of the diaphragm 31 to the orifice 13 of the first passage 11 is concentrically disposed in the pressure equalizing hole 18. Further, the small diameter portion 43 of the valve actuating member 40 inserted to the orifice 13 is formed narrower than the inner diameter of the orifice 13, so as to allow refrigerant to pass through the orifice 13.
Further, as shown in FIG. 4, the valve actuating member 40 has a retaining ring 60 attached thereto for retaining the seal member 50 in position within the hole 14a resisting the high refrigerant pressure from the first passage 11. An annular groove 41 is formed to the valve actuating member 40, and the retaining groove 60 made of metallic material is elastically fit to the annular groove 41.
A known diaphragm actuating fluid is filled in the upper pressure actuated chamber 32 of the power element portion 30, and the heat of the refrigerant from an evaporator 2 flowing through the second passage 12 is transmitted to the diaphragm actuating fluid through the valve actuating member 40 disposed to pass through the second passage and the pressure equalizing hole 18 communicating with the second passage 12, the top portion 42 and the diaphragm 31.
The diaphragm actuating fluid gasifies in response to the heat being transmitted thereto, and applies pressure to the upper surface of the diaphragm 31. The diaphragm 31 is displaced in the vertical direction by the difference in pressure of the diaphragm drive gas applied to the upper surface thereof and the pressure applied to the lower surface thereof. The vertical displacement of the center portion of the diaphragm 31 is transmitted via the valve actuating member 40 to the valve means 20, and moves the valve means 20 toward or away from the valve seat of the orifice 13. As a result, the flow of refrigerant is controlled.
That is, since the temperature of the low-pressure gas-phase refrigerant exiting the evaporator 2 is transmitted to the upper pressure actuated chamber 32, the pressure in the upper pressure actuated chamber 32 is changed in response to this temperature, and when the temperature at the exit of the evaporator 2 is raised, in other words, when the heat load of the evaporator 2 is increased, the pressure within the upper pressure actuated chamber 32 is increased, and in response, the valve actuating member 40 is driven downward to lower the valve means 20, and as a result, the opening of the orifice 13 is widened.
By this movement, the supply of refrigerant to the evaporator 2 is increased, lowering the temperature of the evaporator 2. Thus, the temperature of the refrigerant exiting the evaporator 2 is lowered. In other words, when the heat load of the evaporator 2 is reduced, the valve means 20 is driven in the opposite direction from that described above, narrowing the opening of the orifice 13, by which the amount of refrigerant supplied to the evaporator 2 is reduced and the temperature of the evaporator 2 is raised.
According to the prior art expansion valve described above, there is a need to form an annular groove 41 to the valve actuating member 40, and further, there is a need to elastically deform, slide, and fit the retaining ring 60 to the annular groove 41. This not only increases the number of necessary components, but also increases the number of required steps for assembling the valve.